The processes for alkylation of aromatic compounds with a Friedel-Crafts type catalyst, for example, aluminum trichloride, boron trifluoride, sulfuric acid, hydrofluoric acid, phosphoric acid and the like, are known and used commercially. However, the above described catalysts have the disadvantage of causing corrosion of the materials of the process aside from causing problems of elimination of waste products.
Aside from the mentioned catalysts, the use of activated clay and solid zeolite catalysts has been suggested as catalysts suitable for the alkylation of aromatic compounds to form aromatic alkylated compounds. When using solid zeolite catalysts, two modes of operation have been basically described. First, the catalyst can be used as a powder pap in the liquid reagents. This process has disadvantages since it generally requires operating discontinuously instead of continuously and besides it requires expensive filtering and centrifuging units to separate the catalyst from the desired product and from the unreacted compounds. A more commercially feasible technique implies the use of a fixed bed reactor which contains relatively large catalyst particles, through which the reagents are continuously made to pass.
U.S. Pat. No. 4,459,426 proposes the use of zeolite as the alkylation catalyst of benzene with light C.sub.2 -C.sub.4 olefins. Due to the reduced sized of the zeolite pores, around 10 .ANG., they do not allow the diffusion of heavy molecules, thus, the alkylation in the presence of said catalysts can only be carried out with light olefins.
U.S. Pat. No. 3,849,507 proposes the use of a clayish material, activated with mineral acids and subsequently made into pellets, for the alkylation of benzene with olefins with 4 to 8 carbon atoms per molecule.
U.S. Pat. No. 4,046,826 uses a natural or synthetic triooctahedral clay, hectorite type, interchanged with metallic cations, for the alkylation of benzene with heavy olefins, basically 1-dodecene. Chemically, the hectorite used consists of a hydrated magnesium silicate, with small contents of fluorine, lithium, and other metals, the latter in interchange position. The product, be it natural or synthetic, should be previously interchanged with metallic cations which have a high electronegativity, as Al.sup.3+ or Cr.sup.3+ in order to obtain a catalyst with important catalytic activity.
On the other hand, European patent application 83,970 uses for the alkylation of benzene with light olefins, a clay in which pillars of alumina have been anchored inside its laminar structure, as catalyst.
U.S. Pat. No. 3,671,601 developed by C. L. Sanderson and E. S. Sauer and assigned to the Continental Oil Company, describe the production and purification of crude aromatic alkylate (more specifically alkylbenzene) by reaction of an olefin material or a chlorinated paraffin with an aromatic compound (more specifically benzene) in the presence of aluminum halide as a catalyst. In general, the catalyst used is AlCl.sub.3, either in a pure form or, more frequently, in a complex form, with different organic groups. Likewise, the catalyst may be used in a fluidized form or as a fixed bed on a solid support. This process has the problem that it requires a laborious and costly subsequent operation of separation and purification of the obtained alkylbenzene.
Fishel in his U.S. Pat. No. 3,417,148 refers to an alkylation process in which an aromatic compound, for example, benzene, toluene, xylene, etc. is alkylated with an olefin, using a catalyst that consists of crystalline aluminosilicate chemically combined with metallic subfluoride. The compounds which act as olefin include: olefins, acetylene hydrocarbons, alcohols, esters, ethers, and alkyl halides. The metallic subfluorides are described as aluminum monofluoride, silica difluoride, etc.
Another alkylation process is described in the U.S. Pat. No. 4,070,407 of Haag, which implies alkylation of aromatic compounds which takes place by reaction in which the aromatic hydrocarbons react with an alkylation or transalkylation agent, using a catalyst formed by a crystalline aluminosilicate zeolite. Olefins, alkyl halides and alcohols are adequate alkylation agents as well as alkyl hydrocarbons and aromatic polyalkyl.
In U.S. Pat. No. 3,585,253 of S. K. Huang assigned to Monsato Co. there is reference to an integrated process which includes the separation of paraffins, dehydrogenation of paraffins to olefins, alkylation of aromatics with olefins and sulfonation of detergent alkylate. The alkylation phase takes place by reaction of benzene with a mixture of hydrocarbon containing olefins, in the presence of anhydrous HF as the catalyst. The ratio of benzene to olefin is approximately 6:1 and that of HF to olefin is 18:1. The reaction temperature is 50.degree. C. Subsequently the desired alkylbenzene product, aside from the HF, benzene and paraffins which have not reacted are separated from the effluent.
In the process developed by E. R. Fenske, U.S. Pat. No. 3,494,971, assigned to U.O.P. Company the production of a monoalkylated aromatic hydrocarbon adequate for the production of a detergent product is described. The alkylation between the aromatic compound and the linear monoolefin hydrocarbon takes place in successive steps and uses hydrogen fluoride as a catalyst, which may be fresh and/or regenerated, depending on the different steps of the process. The feeding of linear hydrocarbon (10 to 15 carbon atoms per molecule) is made up of a mixture of an excess (90%) of non-dehydrogenated linear hydrocarbons, along with a minor olefin fraction (10%) with approximately 95% monoolefins and 5% diolefins.
The aromatic compound which reacts with the hydrocarbon stream, in the presence of HF as the catalyst, is benzene in molar excess over the monoolefin fraction. Two phases are obtained as the reaction production, the one which contains the alkylation catalyst and the ones that contains the hydrocarbons, from which are separated on the one part, the HF catalyst which is partly regenerated and on the other part, the unreacted benzene, which is recycled again, the present paraffins (which do not react) and some HF, aside from the desired product, the alkylbenzene. This monoalkylated aromatic hydrocarbon has a bromine index lower than 30 and, typically between 10 and 20.
Many other patents described similar alkylation processes with different types of reagents and which use these same cited catalysts, of the Friedel-Crafts type: hydrofluoric acid (U.S. Pat. No. 3,494,970, U.S. Pat. No. 3,830,865), aluminum trichloride (U.S. Pat. No. 3,631,123, U.S. Pat. No. 3,674,885, U.S. Pat. No. 3,703,559), etc., as well as the clay and zeolite type.
It has been known for quite some time that clay materials have catalytic properties with regard to different organic liquid compounds and that this property varies depending on the type of clay. Over the last 25 years big success has been attained in the production of clay catalysts for the process of cracking oil and for the manufacture of gasolines. At the present time, pillared type clays are being researched as selective catalysts for a certain type of processes (polymerizations) and reactions or large molecules (steroids, antibiotics, etc.) with molecule sizes suitable for their interstices, larger than those of other types of clays and zeolites.
Likewise, it has been described that different materials which contain acidic catalytic points are useful as catalysts of the reaction between aromatic hydrocarbons and different alkylation agents, such as olefins and alkyl halides. See for example: Kirk-Othmer Encyclopedia of Chemical Technology, 2nd. Ed., Vol. 1, pages 882-901 (1963); "Alkylation of benzene with dodecene -1 catalyzed by supported silicotungstic acid," R. T. Sebulsky and A. M. Henke, Ind. Eng. Chem. Process Res. Develop., Vol 10, No. 2, 1971, pages 272-279; "Catalysis by metallic halides, Iv. Relative efficiencies of Friedel-Crafts catalysts in the isomerazation of cyclohexane-methyl-cyclopentane, Alkylation of benzene and polymerazation of styrene," G. A. Russell, J. Am. Chem. Soc., Vol. 81, 1959, pages 4834-4838.
The use of different modified clays has also been proposed as catalysts for different reactions catalyzed by acids, such as alkylation isomerization and the like. See for example the different U.S. Pat. Nos.: 3,665,778, 3,665,780, 3,365,347, 2,392,945, 2,555,370, 2,582,956, 2,930,820, 3,360,573, 2,945,072 and 3,074,983. The last patent describes the use of hectorite clay as a catalyst. Other references which describe the use of clays as catalysts are the following: "Acid Activation of some bentonite clays," G. A. Mills, J. Holmes and E. B. Cornelius, J. Phy. & Coll. Chem., Vol. 54, pages 1170-1185 (1950); "H-ion catalysis with clay," N. T. Coleman and C. Mc Auliffe, Clays and Clay Minerals, Vol. 4, pages 282-289 (1955) "Clay minerals as catalysts," R. H. S. Robertson, Clay Mineral Bulletin, Vol. 1, No. 2, pages 47-54 (1948); "Catalytic decomposition of glycerol by strata silicates," G. F. Walker, Clay Minerals, Vol. 7, page 111-112 (1967); "Polymerization of styrene with interchanged cation aluminosilicates," T. A. Kusnitsyna and V. M. Brmolko, Vysokomol. Soedin, Ser. B 1968, Vol. 10, No. 10, pages 776-9 See Chem Abstracts 70:20373 x (1969); "Reactions catalyzed by minerals. Part I. Styrene polymerization," D. H. Solomon and M. J. Rosser, J. Applied Polymer Science, Vol. 9 1261-1271 (1965.)
As it can be easily seen from the above, there is abundant research under way to obtain catalysts and new processes and more efficient ones for the production of alkylated aromatics, from olefins and aromatic compounds.
Consequently, an improved process for the alkylation of aromatic compounds is an object of the present invention.
Additionally, it is an object of the present invention to furnish a process of alkylation of benzene with C.sub.2 -C.sub.20 range monoolefins, using a solid catalyst of a suitable porosity and activity, in a fixed bed, which provides important advantages over the normal methods, which use liquid catalysts or else solid ones of different structure and features.
Other objects and advantages of the invention will be inferred from the following description.